This invention relates to head shells for record player tonearms.
The recent trend of tonearms for record players is directed toward a reduction of the mass and an increase of the compliance of a vibration system in order to enhance the trackability of a cartridge.
With the compliance of a cartridge increased, the low range resonance frequency attributable to the cartridge compliance and the equivalent mass of a tone arm (including the cartridge) at the stylus tip is reduced such that noise signals due to warpage and eccentricity of a record may be often picked up. That is, the increased compliance results in a reduced signal-to-noise ratio. It is therefore necessary to adjust low range resonance to an inoffensive level, generally to a range of 10 to 15 hertz while the stylus equivalent mass is kept low.
To reduce the equivalent mass at the stylus tip, in usual practice, tonearm component parts such as arm pipe and head shell may be reduced in weight. Parts having a wall thickness reduced for light weight exhibit a low rigidity which in turn, allows undesirable phenomena such as partial vibration to occur, resulting in deteriorated sound quality. To obtain light weight arm pipes and head shells having a high rigidity, materials are required having a high specific modulus of elasticity.
In prior art arm pipe and head shell manufacture, aluminum and titanium are used because they have a relatively high specific modulus. However, the use of a cartridge with an increased compliance requires the arm pipes and head shells to be made of material having a higher specific modulus than aluminum and titanium.
Arm pipes and head shells made of fibrous carbon are known. Fibrous carbon itself has a sufficiently high specific modulus while it cannot be formed into a part without a binder. Usually, a resin is used to bind fibrous carbon. However, the addition of a resin binder to fibrous carbon causes the specific modulus of elasticity to reduce to a level equal to or less than those of aluminum and titanium. Therefore, the fibrous carbon composite material is not satisfactory as the material for arm pipes and head shells.